Browsing by Issue Date, starting with "1997-09-30"

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Effect of lateral substituents on the mesomorphic properties of side-chain liquid crystalline polysiloxanes containing 4-[(S)-2-methyl-1-butoxy]phenyl 4-(alkenyloxy)benzoate side groups
(1997-09-30)
Hsu, CS
;
Chu, PH
;
Chang, HL
;
Hsieh, TH
;
交大名義發表
The synthesis of side-chain liquid crystalline polysiloxanes containing either 4-[(S)-2-methyl-1-butoxy] phenyl 4-(alkenyloxy)benzoate or laterally fluoro-, chloro-, bromo-, and methoxy-substituted 4-[(S)-2-methyl-1-butoxy] phenyl 4-(alkenyl oxy)benzoate mesogenic side groups is presented. The mesomorphic properties of the synthesized polymers have been characterized by optical polarizing microscopy, differential scanning calorimetry, and X-ray diffraction measurements. The effects of spacer length and lateral substituent on the mesomorphic properties of the obtained polymers are examined. The five polymers which contain three methylene units in the spacers show no mesophase, while the five polymers which contain eleven methylene units in the spacer display smectic mesomorphism. Among the other fifteen polymers which contain respectively four, five, or six methylene units in the spacers, those with small fluoro and chloro substituents reveal respectively an Sd phase, while those with bulky bromo and methoxy substituents show no liquid crystalline behavior. The experimental results demonstrate that introducing a bulky lateral substituent into the mesogenic core of a polymer depresses the tendency to form a mesophase. Furthermore, the technique of thermally stimulated current has been used to study the dipolar relaxation mechanisms in a side-chain liquid crystalline polysiloxane. (C) 1997 John Wiley & Sons Inc.
The epoxy-polycarbonate blends cured with aliphatic amine .2. Thermal and mechanical properties mechanisms
(1997-09-30)
Lin, ML
;
Chang, KH
;
Chang, FC
;
Li, MS
;
Ma, CCM
The transamidation reaction converts the carbonate and amine into N-aliphatic aromatic carbamate and urea, causing the equivalent of oxirane and amine nonstoichiometric in the primary cure stage. After postcure, the substitution reaction takes place and results in a more tightly crosslinked structure. Such a higher crosslinking density is responsible for higher T-g, tensile strength, and tensile modulus in the postcure stage than that in the primary and secondary cure stages. This trend is more pronounced in those PC-epoxy blends containing higher molecular weight aliphatic amine or a higher content of PC. This phenomenon is due to the difference in the fraction of amino group of aliphatic amine consumed in the transamidation. PC-epoxy/aliphatic amine blends show minor improvement in the high strain rate Izod impact tests, while toughness improvement for some blends is substantial at low strain rate tensile tests. (C) 1997 John Wiley & Sons, Inc.
The epoxy-polycarbonate blends cured with aliphatic amine .1. Mechanism and kinetics
(1997-09-30)
Lin, ML
;
Chang, KH
;
Chang, FC
;
Li, MS
;
Ma, CCM
Reaction mechanism of the PC-epoxy blends cured by aliphatic amine has been investigated by varying PC contents in the blends. The transamidation reaction tends to convert nearly all the carbonates into N-aliphatic aromatic carbamates even at ambient temperature before normal curing. The remaining amine proceeds the normal curing with epoxy at a higher temperature (80 degrees C). For the PC-epoxy/aliphatic amine blend containing 6 wt % PC, the yielded N-aliphatic aromatic carbamate further reacts with amine to produce the urea structure. The urea undergoes substitution reaction with the hydroxyl formed from the normal curing to give the N-aliphatic aliphatic carbamate. For the blend containing 12 wt % PC, the N-aliphatic aromatic carbamate converts into the N-aliphatic aliphatic carbamate via two different routes. For the blend containing lower molecular weight of the aliphatic amine, the N-aliphatic aromatic carbamate reacts with hydroxyl to form the N-aliphatic aliphatic carbamate directly. For the blend containing higher molecular weight of aliphatic amine, the N-aliphatic aromatic carbamate decomposes into the aliphatic isocyanate accelerated by the presence of the residual oxirane. The isocyanate formed then reacts with hydroxyl to yield the N-aliphatic aliphatic carbamate. The activation energy (E-alpha) and preexponential factor (A) of the PC-epoxy/POPDA blends decrease with the increase of the PC content. Kinetic study by thermal analysis by the method of autocatalyzed model is able to correctly predict oxirane conversion vs. time relationship for the neat epoxy/aliphatic amine and the PC-epoxy/aromatic amine systems because the dominant reaction is the normal curing reaction between amine and oxirane. The model fails to predict the PC-epoxy/aliphatic amine system because the system is complicated by several other reactions besides the normal curing reaction. (C) 1997 John Wiley & Sons, Inc.
The epoxy-polycarbonate blends cured with aliphatic amine .2. Thermal and mechanical properties mechanisms
(1997-09-30)
Lin, ML
;
Chang, KH
;
Chang, FC
;
Li, MS
;
Ma, CCM
The transamidation reaction converts the carbonate and amine into N-aliphatic aromatic carbamate and urea, causing the equivalent of oxirane and amine nonstoichiometric in the primary cure stage. After postcure, the substitution reaction takes place and results in a more tightly crosslinked structure. Such a higher crosslinking density is responsible for higher T-g, tensile strength, and tensile modulus in the postcure stage than that in the primary and secondary cure stages. This trend is more pronounced in those PC-epoxy blends containing higher molecular weight aliphatic amine or a higher content of PC. This phenomenon is due to the difference in the fraction of amino group of aliphatic amine consumed in the transamidation. PC-epoxy/aliphatic amine blends show minor improvement in the high strain rate Izod impact tests, while toughness improvement for some blends is substantial at low strain rate tensile tests. (C) 1997 John Wiley & Sons, Inc.
The epoxy-polycarbonate blends cured with aliphatic amine .1. Mechanism and kinetics
(1997-09-30)
Lin, ML
;
Chang, KH
;
Chang, FC
;
Li, MS
;
Ma, CCM
Reaction mechanism of the PC-epoxy blends cured by aliphatic amine has been investigated by varying PC contents in the blends. The transamidation reaction tends to convert nearly all the carbonates into N-aliphatic aromatic carbamates even at ambient temperature before normal curing. The remaining amine proceeds the normal curing with epoxy at a higher temperature (80 degrees C). For the PC-epoxy/aliphatic amine blend containing 6 wt % PC, the yielded N-aliphatic aromatic carbamate further reacts with amine to produce the urea structure. The urea undergoes substitution reaction with the hydroxyl formed from the normal curing to give the N-aliphatic aliphatic carbamate. For the blend containing 12 wt % PC, the N-aliphatic aromatic carbamate converts into the N-aliphatic aliphatic carbamate via two different routes. For the blend containing lower molecular weight of the aliphatic amine, the N-aliphatic aromatic carbamate reacts with hydroxyl to form the N-aliphatic aliphatic carbamate directly. For the blend containing higher molecular weight of aliphatic amine, the N-aliphatic aromatic carbamate decomposes into the aliphatic isocyanate accelerated by the presence of the residual oxirane. The isocyanate formed then reacts with hydroxyl to yield the N-aliphatic aliphatic carbamate. The activation energy (E-alpha) and preexponential factor (A) of the PC-epoxy/POPDA blends decrease with the increase of the PC content. Kinetic study by thermal analysis by the method of autocatalyzed model is able to correctly predict oxirane conversion vs. time relationship for the neat epoxy/aliphatic amine and the PC-epoxy/aromatic amine systems because the dominant reaction is the normal curing reaction between amine and oxirane. The model fails to predict the PC-epoxy/aliphatic amine system because the system is complicated by several other reactions besides the normal curing reaction. (C) 1997 John Wiley & Sons, Inc.
Effect of lateral substituents on the mesomorphic properties of side-chain liquid crystalline polysiloxanes containing 4-[(S)-2-methyl-1-butoxy]phenyl 4-(alkenyloxy)benzoate side groups
(1997-09-30)
Hsu, CS
;
Chu, PH
;
Chang, HL
;
Hsieh, TH
;
應用化學系
The synthesis of side-chain liquid crystalline polysiloxanes containing either 4-[(S)-2-methyl-1-butoxy] phenyl 4-(alkenyloxy)benzoate or laterally fluoro-, chloro-, bromo-, and methoxy-substituted 4-[(S)-2-methyl-1-butoxy] phenyl 4-(alkenyl oxy)benzoate mesogenic side groups is presented. The mesomorphic properties of the synthesized polymers have been characterized by optical polarizing microscopy, differential scanning calorimetry, and X-ray diffraction measurements. The effects of spacer length and lateral substituent on the mesomorphic properties of the obtained polymers are examined. The five polymers which contain three methylene units in the spacers show no mesophase, while the five polymers which contain eleven methylene units in the spacer display smectic mesomorphism. Among the other fifteen polymers which contain respectively four, five, or six methylene units in the spacers, those with small fluoro and chloro substituents reveal respectively an Sd phase, while those with bulky bromo and methoxy substituents show no liquid crystalline behavior. The experimental results demonstrate that introducing a bulky lateral substituent into the mesogenic core of a polymer depresses the tendency to form a mesophase. Furthermore, the technique of thermally stimulated current has been used to study the dipolar relaxation mechanisms in a side-chain liquid crystalline polysiloxane. (C) 1997 John Wiley & Sons Inc.
Determination of puerarin, daidzein, paeoniflorin, cinnamic acid, glycyrrhizin, ephedrine, and [6]-gingerol in Ge-gen-tang by micellar electrokinetic chromatography
(1997-09-30)
Huang, HY
;
Hsieh, YZ
;
應用化學系
;
Department of Applied Chemistry
This paper presents a micellar electrokinetic chromatography (MEKC) method with diode-array detection to analyze for seven major components in the traditional Chinese medicinal preparation of Ge-gen-tang. Those analytes were successfully separated within 9 min using a pH 9.0 berate buffer containing 20 mM Sodium dodecyl sulfate at 30 degrees C. Experimental results indicated that the relative standard deviations of the analytes' migration times were <0.43% and the correlation coefficients of the analytes' linear calibration graphs exceeded 0.996. The quantities of the seven components in four different Ge-gen-tang samples were determined by the MEKC method coupled with a relatively simple extraction method. (C) 1997 Elsevier Science B.V.
Lifetime and compactness of range for super-Brownian motion with a general branching mechanism
(1997-10-01)
Sheu, YC
;
交大名義發表
;
應用數學系
;
National Chiao Tung University
;
Department of Applied Mathematics
Let X be a super-Brownian motion with a general (time-space) homogeneous branching mechanism. We study a relation between lifetime and compactness of range for X. Under a restricted condition on the branching mechanism, we show that the set X survives is the same as that the range of X is unbounded. (For alpha-branching super-Brownian motion, 1 < alpha less than or equal to 2, similar results were obtained earlier by Iscoe (1988) and Dynkin (1991).) We also give an interesting example in that case X dies out in finite time, but it has an unbounded range. (C) 1997 Elsevier Science B.V.
Plasma transferred are repair welding of the nickel-base superalloy IN-738LC
(1997-10-01)
Su, CY
;
Chou, CP
;
Wu, BC
;
Lih, WC
;
機械工程學系
Plasma transferred are welding (PTA) has been considered a promising process tea restore worn areas of land-based gas turbine blades and vanes. The objective of this investigation was to study the effect of PTA welding on the repairing of IN-738LC superalloy components, Tensile tests were conducted on specimens welded with various combinations of parameters, Room temperature, 760 degrees C, and 980 degrees C were selected Its tensile test temperatures, High-temperature phase transformed, during solidification, were identified by differential thermal analysis (DTA), The weld-pool shapes and microstructures of welded specimens prepared by various welding parameters were evaluated by optical metallography (OM), a scanning electron microscope (SEM) equipped with energy dispersive x-ray spectrometer (EDS), and microhardness testing. Results of this study showed that PTA welded specimens exhibited 96% nominal tensile strength of IN-738LC base materials, Specimen failure was observed predominantly in the base materials instead of in the heat-affected zone (HAZ) for gas tungsten are weld (GTAW) repair weldments, IN-738LC is considered susceptible to weld cracking during fusion welding; however, using a low-input heat repair welding process (PTA), cracking susceptibility could be minimized by the optimized welding parameters.
Transformation models for interval scale grouped data with applications
(1997-10-01)
Lu, HHS
;
Hsieh, FS
;
統計學研究所
;
Institute of Statistics
Interval scale grouped data have peculiar structures of their own rights among various archetypes of polytomous data that deserve special statistical treatments. Maximum likelihood type approaches along with heteroscedastic and transformation models are adapted to take into account this kind of architecture with current state-of-art computation capabilities. Meanwhile, misclassification rates instead of sum of squared residuals are suggested for model fitting and selection in light of the data formation. Successful applications of these methods are demonstrated by a set of empirical data regarding the endotracheal tube size selection for small children in the emergency room of a hospital.
A new power collection architecture for future spacecraft
(1997-10-01)
Kuo, MY
;
Kuo, MS
;
Kuo, CC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The generalized tree-like transmission line network system having n layers in total with m-to-1 branch connection at each joint (T-TLNS-n-m) is proposed to replace the traditional series-parallel combined dc networks to automatically accumulate identically distributed power cells into the large amount of useful power for the spacecrafts, The proposed system has the attractive features of simple structure, easy construction and maintenance, and low cost, because two kinds of parts, ac current sources and m-to-1 transmission line (TL) branch connection parts, are used in the whole system. A method of implementing ac current cells having high output impedance is proposed to improve the power collection efficiency of the whole network system. Simulated results show that that low-pass nominal pi- or T-circuit with high characteristic impedance, which is used for the voltage source to current source converter in the current cell, improves the efficiency of the voltage inverter, filters out the harmonics, and increases the output impedance of the whole current cell.
Design of a rule-based flexible manufacturing system controller using modified IDEF0 methodology
(1997-10-01)
Chen, SG
;
Wu, MZ
;
Li, RK
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
This article proposes a new method to design a rule-based FMS controller. This approach adopts modified IDEFO (MI) diagrams as a graphical representation of the production rules. Initially, the material flows or functional requirements for the FMS are specified by synthesizing the MI diagram primitives. The control flows for the FMS are then created by a number of transformation rules. The manufacturing policy, e.g. deadlock avoidance policy, is also specified and attached. The MI diagrams are therefore transformed to the final MI (FMI) diagrams which can be directly transformed to the production rules. Thus, a concise rule-based FMS controller is developed. The fact that the production rules are created by systematic transformation eliminates any redundant, contradictory, or unnecessary rules. Two approaches can verify the consistency of the designed FMS controller. The controlled Petri net approach can be adopted for verifying a small system, while a simulation approach is preferable for verifying a large system. By iterating the process, a feasible rule-based FMS controller can be systematically developed. This method not only provides graphical representations to construct well-organized production rules, but also includes a systematic transformation of the control flows for an FMS controller.
Phase diagram of crystals of dusty plasma
(1997-10-01)
Lee, HC
;
Chen, DY
;
Rosenstein, B
;
電子物理學系
;
Department of Electrophysics
Dust particles effectively charged by plasma recently have been optically observed to exhibit crystalline phases not expected of Wigner or Yukawa crystals. Under varying conditions the crystal sometimes appears as deformed and oriented three-dimensional close-packed lattices of bcc, fcc, or hcp type, but mostly as a triangular array of vertical chains of particles. The unusual phases are shown to be caused by dipole-dipole interactions. The dipole moments are induced on the dust particles by gravity and by drag forces generated by ion stream. We describe in detail stable lattice structures and present the highly complex phase diagram of the dusty plasma. It turns out that in large parts of the phase diagram the stable phases indeed correspond to chains, but particles in neighboring chains belong to different sublattices. The stability of the lattices against excitations due to compression (i.e., aspect ratio variations) and vibration (i.e., phonons or charge density waves) is established.
Signed degree sequences of signed graphs
(1997-10-01)
Yan, JH
;
Lih, KW
;
Kuo, D
;
Chang, GJ
;
應用數學系
This paper gives necessary and sufficient conditions for an integral sequence to be the signed degree sequence of a signed graph or a signed tree, answering a question raised by Chartrand et al. (1994). (G. Chartrand, H. Gavlas, F. Harary, and M. Schultz, On signed degrees in signed graphs, Czech. Math. J.44 (1994), 677-690). (C) 1997 John Wiley & Sons, Inc.
Mode distinction and radiation-efficiency analysis of planar leaky-wave line source
(1997-10-01)
Lin, YD
;
Sheen, JW
;
交大名義發表
;
傳播研究所
;
National Chiao Tung University
Using the first microstrip-line higher order mode as an example, mode distinction and radiation efficiency of leaky-wave line sources in the radiation region are presented in this paper, The spectral-domain approach is used to calculate complex power hows, leaving the line source in the transverse directions and those guided down the line source. Ply observing the behavior of these complex power flows in different frequency regions, the leaky-wave line source can be distinguished into the antenna mode and the reactive mode in the radiation region, Experimental results are shown to confirm this mode distinction, Moreover, by comparing the power carried away by the surface and the space waves, radiation efficiency of the first microstrip-line higher order mode of various structural parameters is analyzed. The microstrip line is more efficient as a leaky-wave line source when its substrate is thin, the dielectric constant of the substrate is low, and the antenna main,cam is away from the end-fire direction.
The instability characteristics of amorphous silicon thin film transistors with various interfacial and bulk defect states
(1997-10-01)
Cheng, HC
;
Tsai, JW
;
Huang, CY
;
Luo, FC
;
Tuan, HC
The instability characteristics of hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFTs) with various interfacial and bulk defect states were systematically investigated. It was found that, under positive bias stresses; the threshold voltage shifts of a-Si:H TFT's with the same interfacial defect states but with different bulk defect states exhibited similar threshold voltage shift characteristics. In contrast, a-Si:H TFTs with different interfacial defect states but the same bulk defect states showed threshold voltage shifts proportional to the interfacial defect states under positive bias stresses. Furthermore, both the above kinds of a-Si:H TFT under positive bias stresses exhibited that the subthreshold swing shift characteristics closely related to both the interfacial and bulk defect states.
Implementation of an active headset by using the H-infinity robust control theory
(1997-10-01)
Bai, MS
;
Lee, D
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
This paper presents a methodology for implementing an active headset by using H-infinity robust control theory. The adopted structure is feedback tracking control. Performance, stability, and robustness of the closed-loop system have been taken into account in the design procedure by using a general framework of the H-infinity theory. The resultant controller is realized on the basis of operational amplifier circuitry. Experiments are conducted to test the developed headset. The result shows that the headset achieves broadband attenuation up to approximately 15 dB in the band 200-800 Hz. The design considerations indicated in the experimental result are also addressed. (C) 1997 Acoustical Society of America. [S0001-4966(97)05709-3] PACS numbers: 43.50.Ki, 43.38.Si [GAD].
Transformation models for interval scale grouped data with applications
(1997-10-01)
Lu, HHS
;
Hsieh, FS
;
統計學研究所
;
Institute of Statistics
Interval scale grouped data have peculiar structures of their own rights among various archetypes of polytomous data that deserve special statistical treatments. Maximum likelihood type approaches along with heteroscedastic and transformation models are adapted to take into account this kind of architecture with current state-of-art computation capabilities. Meanwhile, misclassification rates instead of sum of squared residuals are suggested for model fitting and selection in light of the data formation. Successful applications of these methods are demonstrated by a set of empirical data regarding the endotracheal tube size selection for small children in the emergency room of a hospital.
Clustered affinity scheduling on large-scale NUMA multiprocessors
(1997-10-01)
Wang, YM
;
Wang, HH
;
Chang, RC
;
資訊工程學系
;
Department of Computer Science
Modern shared-memory multiprocessors have high and non-uniform memory access (NUMA) costs. The communication cost gradually dominates the source of parallel applications' execution. Algorithms based on affinity, like affinity scheduling algorithm (AFS), perform better than dynamic algorithms, such as guided self-scheduling (GSS) and trapezoid self-scheduling (TSS). However, as the number of processors increases, AFS suffers heavy overheads for migrating workload. The overheads include remote reads to the queues for the indices information, synchronous writes to the queues for migrating iterations, and the time in loading data into cache. In this paper, we propose a new loop scheduling algorithm, clustered affinity scheduling (CAFS), to improve affinity scheduling algorithm. We distribute the processors into several clusters, and cluster-based migrations are carried on when imbalance occurs. We confirm our idea by running many applications under a realistic hierarchy memory simulator. Our results show that CAFS reduces at least 1/3 of both remote reads and synchronous writes to the queues under most applications. CAFS also improves the cache hit ratios, and balances the workload. Therefore, we conclude that under large NUMA multiprocessor, CAFS is a better choice among loop scheduling algorithms. (C) 1997 Elsevier Science Inc.
Modelling and measurement of UHF radio propagating through floors in a multifloored building
(1997-10-01)
Tarng, JH
;
Perng, DW
;
電信工程研究所
;
Institute of Communications Engineering
A general three-dimension theoretical model is developed to predict the path loss of UHF radio propagation through floors in a multifloored building. The computed propagation loss is compared with the measured value of 900 MHz, 1.4 GHz, 1.9 GHz, and 2.44 GHz and gives a reasonable agreement. It is found that the floor, lateral beams and the walls around the receiver are the major construction features to affect the estimation of the penetration loss through floors.